"It was very much a shunt type incident and it left a train of debris across the motorway."

It is understood that one of those airlifted to hospital was a man who was struck by another vehicle after getting out of his car. He is reported to have suffered head and leg injuries.

The second person taken from the scene by helicopter, a woman in her 20s, was suffering from breathing difficulties after sustaining chest injuries. The five other injuries were not serious.

The northbound M6 was closed after the incident, which happened about 10.45am.

The Central Motorway Police Group said the accident happened yards from the exit slip-road at junction 16, which straddles the border between Staffordshire and Cheshire.

Diverted traffic left the motorway at the junction 16 exit, and rejoined it from the slip-road entrance at the same junction.

A spokesman for Cheshire Police said they had been forced to close the southbound carriageway to allow the air ambulance to land and take the seriously injured to hospital, and jams continued to stretch along the motorway into yesterday afternoon.

The section of motorway was eventually reopened shortly after 3.30pm, after all the vehicles had been recovered.

He said: "On the southbound carriageway there were delays because people were slowing down to look, causing danger to themselves and other people around them. It's totally unnecessary."

Among those caught up in the disruption were Liverpool fans travelling to the Boxing Day fixture against West Bromwich Albion.

It is not yet clear if icy conditions caused the accidents, but the emergency services warned drivers to take extra care in the cold weather.